1. Field of the Invention
The present invention relates to a wing structure of an aircraft, wherein a plurality of spars extend in a span direction; a plurality of stringers are arranged between the spars and extend in the span direction, a rib extends in a chord direction to connect the spars to each other and skins are provided for covering upper and lower surfaces of the spars, the stringers and the rib.
2. Description of Related Art
A wing structure of aircraft is known as described in Japanese Patent Application Laid-open No. 2002-302097 and Published Japanese Translation No. 2000-506816 of PCT Application No. PCT/US97/04550.
More specifically, a rib defining the airfoil of an aircraft wing is formed by press molding a thin plate-shaped material for weight reduction. Stringer through holes are formed on the upper and lower edges of the rib, and stringers are fixed on the inner surfaces of the skins of the wing and are passed through the stringer through holes with a gap therebetween. The wing has a box structure having a resistance against bending and torsion, and includes spars, stringers, ribs and skins connected to each other. However, when a lift or a drag acts on the wing, there is a possibility that the rib formed of a thin plate-shaped material is buckled by a shear load. To solve this problem, in the wing structure described in Japanese Patent Application Laid-open No. 2002-302097 or Published Japanese Translation No. 2000-506816, a bead extending in the vertical direction (wing thickness direction) is formed integrally on the rib when the rib is press-molded, thereby increasing the buckling strength of the rib against the shear load.
However, it is difficult to compensate for the reduction in strength of the rib due to stringer through holes formed therein, merely by forming the bead extending in the vertical direction (wing thickness direction) on the rib. In order to secure a sufficient strength, the wall thickness of the rib is required to be increased along with an increase in the weight.